This invention relates to methods and apparatus for packaging can ends, e.g. disc-like end units which have a preparatory curl on their edge and which may also have attached easy-open tabs. In practice such apparatus is often called a bagger, since the preferred manner of packaging the ends places a stack (usually called a xe2x80x9cstickxe2x80x9d) of the ends in a tubular bag which is then folded closed at its initially open end.
In the early 1970s can ends were placed manually into bags, and the bags were loaded manually into pallet for use at filing/closing machinery. In the mid-1970s semi-automatic bagging equipment was introduced in an effort to keep up with the increased output of newer conversion presses, and that development led to automatic bagging machines, which were first introduced in the mid-1980s. Some of the impetus for this development was the monotony of repeated manual operations, which also appeared to be the cause of repeated strain to the hands of those doing the bagging.
Those automatic machines formed a xe2x80x9cstickxe2x80x9d of ends and then packaged them 1) by wrapping them from a coil or reel of paper or plastic, or 2) placing the sticks into preformed bags. It was found that kraft paper was the preferred wrapping material since it can be recycled, and since it will xe2x80x9cbreathexe2x80x9d to void fumes which may linger with the stick of ends from synthetic sealing compounds applied to the ends in an earlier operation, or to void moisture which may linger from water based compounds.
In the early patent prior art, the disclosures in U.S. Pat. Nos 3,337,064, 3,417,853, 3,545,631 and 3,618,530 are representative of systems which use a pneumatic or similar input conveying system for the individual can ends, and troughs or the like for gathering the ends in a face to face on-edge stack. Mechanical feeding mechanisms engage the curl edges of the generally vertically positioned ends and move them into the input or receiving end of a stack forming in a trough, then the ends are supplied to a filling and closing (end curling) machine. Wrapping a stack is not disclosed, and the filled trough is intended to function as a reservoir for smooth steady supply of ends to the closing machine.
In U.S. Pat. Nos. 3,722,741, 4,000,709, 4,537,550, 4,676,708 and 5,335,810 more sophisticated buffer systems for stacks of ends are disclosed, wherein the stacks are separated according to a count of stacked ends, and those stacks are loaded into successive vertically arranged carriers on an endless, carrousel-type conveyor which supplies the stacks to a closing machine.
U.S. Pat. No. 3,878,945, and its various divisions Nos. 3,962,845, 3,971,189, 4,051,965, and U.S. Pat. No. 5,119,617, all disclose features of an automatic bagging system in which ends are supplied to a gathering and counting deice which separates ends into stacks (or xe2x80x9csticksxe2x80x9d), wrapping devices for loading the stacks into individual bags, and mechanism for loading the wrapped stacks onto pallets.
U.S. Pat. No. 4,364,255 relates to a conveying improvement for gathering ends, providing temporary spacing thereof to facilitate curing of previously applied end seam compound. U.S. Pat. No. 4,655,350 discloses an improvement for detecting and removing ends which have been reversed factoback (e.g. public to product sides) in the formation of a stack. U.S. Pat. No. 4,742,669 discloses an improved end counting device in the end counting and stack forming systems. U.S. Pat. No. 5,005,340 discloses a system for inspecting an assembled stack of ends. U.S. Pat. No. 5,372,245 discloses an improved drive for an in-feeding array of assembled ends. U.S. Pat. No. 5,524,947 discloses an improved mechanism for picking and placing stacks (also called xe2x80x9csticksxe2x80x9d) of ends in the bagging and palletizing process.
U.S. Pat. Nos. 4,537,010 and 5,372,473 disclose more advanced devices for handling bagged stacks of ends and placing them into pallets.
Thus, prior art automatic bagging machines allow lanes of ends from the output of a conversion press to be counted, separated in stacks or sticks, the stacks placed into individual bags, and the bagged stacks are then loaded into a common palletizer, from which a supply is provided Go one or more filling and closing devices.
According to this invention each stick of ends contains an exact count of ends which are separated from the incoming stream of ends, and that dimension, as well as the orientation of the stick, is maintained through processing in the novel automatic bagger provided by the invention. The loading operation, moving the stick of ends into an open ended bag, is controlled such that sponginess of the assembled stick is taken into account, and the bags will not be overfilled. On the other hand, under filled bags will be rejected. The sponginess results primarily from variations in compression of the curl ends (rims) of the ends pressing against each other in the gathering and counting process.
The loader mechanism includes a servo controlled pusher which is driven with controlled acceleration and deceleration to avoid bursting of the bags during filing, while assuring complete and uniform filling of each bag.
An improved can end bagging system according to the invention comprises four subassemblies or subsystems, 1) the end gathering and stick assembly (or formation) apparatus, 2) the bag feeding, opening, and loading apparatus which places a predetermined number (to comprise a complete stick) of stacked can ends into an open end bag, 3) the vertical positioner apparatus for moving the bagged sticks into a folding device, and 4) the bag folding, closing and transfer apparatus.
Once the closed stick is sealed, it is transferred into a gathering mechanism in the palletizer section of the system, maintaining a predetermined orientation of the bag, until a desired number of bags are assembled on a transport carrier tray. That number of bags is determined by the number of bags desired as making up a horizontal row on a pallet load of the bags.
A palletizing mechanism supplies a pallet (support) and a length of wrapping paper (usually Kraft paper or the like) for receiving successive rows of bags and intertwining rows until a full pallet load is prepared. Details of this operation are disclosed in copending International Application No. PCT/US98/20409.